Drum type heat transfer apparatus



April 13, 1965 H. SMITH, JR

DRUM TYPE HEAT TRANSFER APPARATUS 3 Sheets-Sheet 1 Filed June 24, 1963 HORACE L. SMITH, JR.

ATTORNEYS A ril 13, 1965 Filed June 24, 1963 H. L. SMITH, JR 3,177,932

DRUM TYPE HEAT TRANSFER APPARATUS 3 Sheets-Sheet 2 INVENT OR HORACE L. SMITH, JR.

BY MM, MQ M ATTORNEYS April 13, 1965 H. L. SMITH, JR 3,177,932

DRUM TYPE HEAT TRANSFER APPARATUS Filed June 24, 1963 3 Sheets-Sheet. 3

INVENTOR HORACE L. SMlTH, JR.

MM, 72%,, a M

Arromvsvs h C 2L |l \M N E 3m\ H 4 5n w o Il flw wg ui g, w K 8 r H OW N b all n w y 1Q .lllllllliilll s v25 inu /\om II III II II 2 1 h United States Patent 3,177,932 DRUM l YPE i EAT TRANdFER APPARATUE: Horace L. Smith, Era, Richmond, Va, assigner to Hupp Corporation, Cleveland, Ohio, a corporation of Virginia Filed June 24, 1%3, Ser. No. 289,935 7 (Ilairns. (Cl. 16533) United States iatent No. 3,061,944 issued November 6,

1962, to l. J. Kraus et al. for Paper Making Machine, the incoming Wet sheet passes around a large pressure roller which presses the sheet against the revolving heated drum, squeezing out undesired fluids and air which would otherwise have a deleterious effect on the final product. Pressure roll loads are normally in the order of iii-15,000 pounds and may, due to the conventional Yankee driers lack of rigidity, deflect the central portion of the surface of the drying drum, causing a non-uniform application of heat and pressure to the tissue paper and a consequent lack of final product uniformity. In an average size Yankee drier the drying drum may be on the order of 14 feet in diameter and 15 feet long and the deflection caused by the pressure roller may be as great as 0.055 inch.

Another disadvantage of conventional Yankee driers is that their surface temperatures vary from place to place on the drum surface. Non-uniform surface temperatures also cause undesirable variances in the quality of the final product since the non-uniform temperatures cause differential heat losses, resulting in uneven drying of the product.

A third disadvantage of conventional Yankee driers is that steam is employed as the heating medium. To achieve even a minimal drying rate, the steam must be heated to a temperature on the order of 350 F. At this temperature steam has a vapor pressure of 135 p.s.i.a. This pressure is sufiiciently high to require expensive, heavy duty system components in order to provide an adequate safety factor.

Numerous attempts have been made to increase the resistance of the drying drum to pressure roll deflection and to increase the uniformity of the drums surface temperature. The most successful of the improved prior art drum driers is that shown in my copending application No. 118,439, filed June 20, 1961, for Heat Transfer and Pressure Applying Apparatus and Method of Manufacture Thereof. The present invention represents an improvement over the drum drier disclosed in my previous application. It is substantially simpler and more economic to manufacture than the drier disclosed in my previous application, provides a more uniform surface temperature and has a substantially higher resistance against pressure roller induced deflection 0f the drum.

In general, the novel drum drier of the present invention includes concentrically disposed inner and outer shells separated by longitudinally extending, radially oriented, equiangularly spaced partitions. The trapezoidally sectioned passages between the partitions are connected by appropriately shaped conduits into two or more independent, internested, labyrinthine independent flow channels extending around the periphery of the drum. A novel heat transfer fluid supply and return system is employed to introduce heat transfer fluid into and cause it to flow in opposite directions through the two channels.

Preferably, the locations at which the heat transfer fluid is introduced into and removed from the flow chan- 3,177,932 Patented Apr. 13, 1%65 ice nels are so selected that the distance through which the fluid flows in the two channels is substantially equal. Heat losses in the two flow channels will thereby be Substantially equal; and, in addition, the hotter legs of one channel will be disposed adjacent the cooler legs of the other channel. As a result, the temperatures in adjacent channels will tend to equalize and the entire surface of the outer shell will be maintained at a highly uniform temperature.

Further benefits of this novel construction are that: (l) the resulting drum drier structure is substantially more resistant to pressure roller induced deflection than any drum drier heretofore provided; and (2) the novel drum driers provided by the present invention are substantially simpler and more economical to fabricate than those of the prior art.

'Preferably, the novel drum driers of the present invention are heated by certain liquid hydrocarbons which may be heated to temperatures of 500800 F. and higher without boiling or decomposing to a significant extent. The heat transfer medium is circulated in liquid form at low pressure, eliminating the disadvantages attending high temperature steam and yet permitting higher surface temperatures to be attained than is practical in steam heated drum driers.

It is a primary objectof the present invention to provide novel, improved drum driers.

Another object of the present invention resides in the provision of drum driers which are substantially simpler and more economical to construct than those presently available.

Yet another object of the present invention resides in the provision of drum driers which are substantially more rigid and resistant to pressure roller induced deflections than those of the prior art.

Another important object of the present invention is the provision of drum driers having more uniform surface temperatures than has heretofore been possible.

In conjunction with the preceding object, it is a further specific object of the present inventionto provide drum driers having a multiplicity of internested, labyrinthine flow channels through which heat transfer liquid may be circulated in opposite directions to increase the uni-. formity of 'the drums surface temperature.

A further object of the present invention resides in the provision of novel, improved drum dr'iers adapted to be heated by a circulating liquid heat transfer medium to temperatures several hundred degrees higher than -is possible in conventional steam heated'drum driers.

Further objects and other novel features of the present invention will become more fully apparent from the appended claims, and as the ensuing detailed "description and discussion proceeds in conjunction with the accompanying drawing, in which:

FIGURE 1 is a longitudinal section through a drum rier constructed in accordance with the principles of the present invention, illustrating the fluid supply and return systems and their physical relation to the labyrinthine flow channels adjacent the periphery of the drier;

FIGURE 2 is a section through the drier of FIGURE 1, taken substantially along line 2-2 of the latter figure, showing the interrelation of the fluid return system, the flow channels, and the U-shaped tubes employed to transfer fluid between legs of the flowchannels;

FIGURE 3 is a view similar to FIGURE 2, taken substantially along line 3-.3 of FIGURE 1, showing the V interrelation of the fluid supply system, the flow channels, and the fluid transfer tubes;

FEGURE 4 is a perspective view of one of the U- shaped fluid-transfer tubes employed in the drier of FIG- URE 1; v

FIGURE 5 is a section through the drier of FIGURE 1 taken substantially along line 55 of the latter figure, illustrating portions of the fluid supply and return system, the inner and outer drum shells, and the radially oriented partitions by which they are separated; and

FIGURE 6 is a development of the flow channels.

Referring now to the drawing, FIGURE 1 shows a rotatable drum drier 10 having an outer cylindrical shell 12 of heat conductive material, preferably cast iron, and an inner cylindrical steel shell 14 separated by longitudinally extending, radially oriented, steel partitions 16 connected by U-shaped tubes 18 into two internested, labyrinthine, flow channels 20 and 22. A fluid supply and return system 24 delivers a heated, preferably liquid, heat transfer medium to and causes it to flow in opposite direction through two independent flow channels, thereby effecting a substantially uniform distribution of heat to the external surface 28 of outer drier shell 12.

One of the novel features of the present invention resides in employing a high boiling point hydrocarbon liquid as the circulating medium, permitting it to be circulated at extremely high temperature in liquid form and under low pressures. Consequently, drum drier It may be heated to high temperatures and yet it and the other heating system components need be designed to withstand only very low pressures. Preferred heat transfer liquids includes Arcolor 1248 (a chlorinated biphenyl) and Isopropyl Santowax (a polyphenyl alkyl), which are produced by Monsanto Chemical Company and XF1-0l84 (an arylaryloxysilane manufactured by Dow Chemical Company). The physical properties and advantages of these liquids and a preferred system for heating and circulating them are discussed in detail in my copending application No. 237,817, filed November 15, 1962, for High Temperature Heating Apparatus to which reference may be had if deemed necessary for an understanding of the present invention.

Referring again to FIGURE 1, outer shell 12, inner shell 14, partitions 16, and a pair of circular end walls 30 and 32 are joined as by welding into a rigid unitary structure which is extremely strong and rigid and highly resistant to pressure roll induced deflections and other loads imposed upon drier10.

Referring now to FIGURE 6, one pair of adjacent partitions, identified by reference character 16a, terminates in spaced relationship to the left-hand end wall 30 of drum drier 10. The adjacent pair of partitions, identified by reference character 16b, terminates in spaced relation ship to the right-hand end wall 32 of the drier. This pat tern is continued around the drum drier, each pair of partitions 16a being separated by a pair of partitions 16!).

As is best shown in FIGURES 2, 3, and 6, flow channel 22 includes alternate straight runs or legs 34a and 34b defined, respectively, by the alternating pairs of partitions 16a and 16b. The U-shaped fluid transfer tubes 18 are connected between each pair of partitions 16a and the adjacent pair of partitions 16b, providing fluid communication between alternatechannel legs 34a and 3411. As shown best in FIGURE 6, the fluid transfer tubes 18 are alternately disposed at opposite ends of drum drier 10 so that the heat transfer medium flows alternately to the left and to the right through legs 34a and 34b, traveling in a labyrinthine or zig-zag throughflow channel 22.

As shown in FIGURE 6, flow path 20 consists of straight runs or legs 36, each of which is disposed between two of the legs 34a and 34b of flow channel 22. By terminating each pair of partitions 16a and 16b short of the end Walls 30 and 32 of drum drier 10, passages 38:: and 38b are alternately provided at opposite ends of drum drier 10 between the U-shaped fluid transfer tubes 18 and the associated ends of the drum drier. These passages allow the fluid in channel 20 to flow around the ends of the tubes so that it alternately flows to the left and to the right through flow channel 20, traveling back and forth in a labyrinthine or zig-zag path around the periphery of the drier.

Turning now to FIGURE 4, the U-shaped fluid transfer tubes 18 may be bent from any appropriate size and type of tubular stock. The fluid transfer tubes each consist of a pair of substantially parallel, spaced apart legs 40 and 42 separated by a semicircular, integral connecting portion 44. Legs 45) and 42 are cut away, providing parallel edges 45 and 46 parallel to the, longitudinal centerlines of the transfer tube legs and a semicircular shoulder or ledge 48 oriented normally to edges 45 and 46.

Referring next to FIGURES 1 and 6, fluid transfer tubes 18 are Welded to drum drier 10 with the upper ends 50 of tube legs 46 and 42 sealed against the outer cylindrical drier shell 12. The edges 45 and 46 of the two tube legs 40 and 42 are welded, respectively, to the juxtaposed ends of a pair of partitions 16a and the juxtaposed ends of the adjacent pair of partitions 16b. The transveresly extending ledges 48 of the tube legs 40 and 42 are flush with the exterior surface 52 of the driers inner cylindrical shell 14 which is provided with suitable apertures 54 through which the lower portions of tube legs 46 and 42 extend. The fluid transfer tubes 13 and inner shell 14- are connected as by welding to form a fluid tight seal.

Referring again to FIGURE 1, the fluid supply and return system 24 includes a pair of axially aligned hollow axles 56 and 58, fixed to drier end walls 30 and 32, by which drum drier 10 is rotatably supported. Fixed to the inner ends of axles 56 and 58 and extending longitudinally of the drier are main supply and main return conduits 6t) and 62 which communicate, at their outer ends, with axial flow passages 64 and 66 through axles 56 and 53. The inner ends of conduits 60 and 62 are joined, at a point somewhat to the left of the longitudinal midpoint of drum drier 10, by a solid cylindrical plug 68 to which they are fixed as by welding.

Referring now to FIGURES 1, 3, and 5, a plurality (four in the illustrated embodiment) of radially extending branch supply conduits 70 communicate with the interior of main supply conduit 60 (to which they are fixed as by welding) adjacent its connection with plug 68. At their outer ends, conduits 70 extend through appropriately sized apertures 72 in drier inner shell 14 (to which they are fixed as by welding), into communication with the flow channels 20. and 22 defined by partitions 16 and fluid transfer tubes 13.

As best shown in FIGURE 6, two of the branch supply conduits, 7041 and 70b communicate with flow channel 20 at locations substantially at the longitudinal midpoint and on opposite sides of drum drier 10. The remaining branch supply conduits 70c and 70d, communicate with flow channel 22, also substantially at the longitudinal midpoint of drum drier 10. As best shown in FIGURE 6, branch supply conduits 70c and 70d communicate with flow channel 22 at points substantially equidistantly spaced between the points at which branch supply conduits 70a and 70b communicate with flow channel '20 so that the circulating heat transfer medium is introduced into the flow channels at substantially the longitudinal midpoint of drum drier 10 and at points substantially equidistantly spaced apart around its circumference.

Four radially extending branch return conduits 74a, 74b, 74c, and 74d are connected between main return conduit 62 and flow channels 20 and 22 in substantially the same manner as branch supply conduits 70ad, and

are separated from the supply conduits by solid plug 68 which prevents fluid from flowing from main supply conduit 60 into main return conduit 62.

As shown in FIGURES 1 and 6, branch return conduits 74a and 74b communicate with flow channel 20 at substantially the longitudinal midpoint of drum drier 10 and on opposite sides thereof. The remaining branch return conduits, 74c and 74d, communicate with flow channel 22- at the drier midpoint and at points substantially equidistant from conduits 74a and 74b around the; circumference of the drier. At their inner ends, branch return conduits 74a-d communicate with the interior of main return conduit 62 to which they are fixed as by Welding.

Referring now to. FiGl-JRES 1 and; 6, the; heated; circulating, fluid. heat-transfer medium; flows into. drum drier ltithrough. the axial passage 66 in axle 58 then through the longitudinally extending main supply conduit 60,.- into the radially oriented branch conduits 7%ia-d. The heat transfer medium then flows outwardly through branch conduits 7tlad. into flow channels and: 2-2, respectively. At the juncture of each branch supply conduit and each flow channel, the stream of liquid flowing into the 01 E 1 nel divides and flows in opposite directions through the channel as shown bythe arrows in FIGURE 5. The circulating medium t-hen flows into branchreturn conduits 74a-d and through main return conduit 62 and the passage 64 in axle 56 to the exterior, ofdrier 14).

As a result of the manner in whichv the heat transfer medium is introduced iutQ, circulated through, and exhausted from drum drier 1t eight flow paths are set up in the drier, four in flow channel 20- and: four in flow channel 22. Two of these flow paths are shown by the full and broken lines, identified by reference characters 76 and 78, respectively, in FIGURE 6. As shown by the solid and broken lines 75 and 78, the fluid flows in opposite directions in adjacent legs of channels 20 and 22, so that there is true counterflow of the heat transfer medium in and throughout the two flow channels.

Moreover, as also shown in FEGURE 6, in each pair of cooperating flow paths, one of which is in each of the two channels 20 and 22, the branch supply conduit 76 (for example 7tid) through which the heated fluid enters one flow path (76 for example) is immediately adjacent the branch return conduit (for example 74b) into which much cooler fluid flowing from the co-operating flow path in channel 22 (in this case 78) is exhausted. Conversely, the cool fluid is exhausted from flow path 76 and flow channel 20 through branch return conduit 74d immediately adjacent the point at which the heated fluid is introdnced into the flow path 78 in flow channel 22 through branch supply conduit 70!). As a result, the two flow paths 76 and 78 have the same length; and, because there is counterflow in the two channels 26 and 22, the hottest fluid in one flow path circulates immediately adjacent the coolest circulating medium in the second flow path.

Heat is transferred from the hotter circulating medium in one channel through the intervening heat conductive partition 16 to the much cooler fluid flowing in the adjacent leg of the other flow channel so that the temperature of the fluid in adjacent legs and at points lengthwise of the drier is equalized and heat is transferred to the outer cylindrical shell 12 of drier 10 at a highly uniform rate throughout its extent. Since outer cylindrical shell 12 is preferably fabricated of a homogeneous material and has a uniform thickness throughout, heat will be transferred from its inner to its outer surface at a substantially uniform rate; and, as a result, the exterior surface temperature of the drum drier will be highly uniform.

Many modifications may be made in the above-described exemplary embodiment of the present invention without exceeding the scope of this invention. For example, flow regulating devices may be employed in the fluid supply and return system 24 to eliminate any minor irregularities in flow rate or to permit flow rates through drier 10 to be varied. As a further example, the number of branch supply and return exhaust conduits 70 and 74 may be varied as desired for particular installations. Further, branch return conduits 74 and branch supply conduits 70 need not be at substantially the longitudinal midpoint of drier 10 as illustrated, but may be located closer to or immediately adjacent end walls 36 and 32 as long as the cooperating; flow paths in channels 2t) and 2 2 are of equal length.

The nve tiou may e emb i n. the p c fic rm th ut dep rt n fr m the pi or se l; charact st c t ere fihe p ent e b d m nt: s the r t e wandere n. a l; r snepts as illust ative and: not restrictive, the scope of the invention being indicated, by t e appe ded; laims. ther t y, the f r g ingv r ption, and; all changes which come. within the meaning and nange of; equivalency, of the claims, are therefore intended to be embraced therein. 7

Whatl imed; and: desir d tovv bev Secured: by. tters Bate-tit; is v a H at xc an e ppa u adapted. to hav a. fluid. h t sfe medium ulated. ther through t hea a external surface of said; apparatus to a uniform predeerm ed smae a uie. mpr n (a) concentric inner and outer shells. of substantially qu qnst t S id he -1 having a uniform. thickness andthe radial distancebetween said; shells. being sub.- staat allu rea e han he. t ickness, of ea f said: shells;-

( first: and e ond. e d a t the pn sit s of and extending between the inner and outer shells, said end walls being fixed to said shells to provide a closed annular passage therebetween;

(c) radially oriented, longitudinally extending partitions which are members separate from said shells between and fixed to said shells, the ends of alternate pairs of said partitions being closely adjacent the first end wall and substantially spaced from the second end wall, and the ends of the pairs of partitions between said alternate pairs being closely adjacent the second end wall and substantially spaced from the first end wall;

(d) a plurality of fluid conducting means in the interior of said outer shell for conducting fluid from the ends of passages formed by the shells and partitions to the next alternate passage and thereby dividing the passages between partitions into two independent labyrinthine flow channels with adjacent passages being in different ones of said flow channels, said fluid conducting means having first and second legs extending through said inner shell and beingin fluid communication with the passage between the partitions in a first one of said pairs and the passage between the partitions in the adjacent one of said pairs, the legs of said fluid conducting means forming closures for the ends of the passages with which said legs communicate, one of said legs being spaced from the nearest end wall and the other of said legs being in contact with the nearest end wall, whereby the passages between adjacent pairs of partitions are serially connected to form one of said channels and the passages between the partitions in the pairs of partitions are serially connected to form the other of said channels;

(e) means for directing fluid to each of said channels; and (1) means for conducting fluid from each of saidchannels.

2. The heat exchange apparatus as defined in claim 1,

wherein the two last-named means comprise a system for delivering to and exhausting from said channels a circulating fluid heat transfer medium, comprising:

(a) a main supply conduit;

(b) a plurality of branch supply conduits communicating between the main supply conduit and each of the flow channels;

I (c) a main return conduit;

(d) a plurality of branch return conduits communicating between each of said channels and the main return conduit;

, (e) the flow paths between the supply and return conduits in one of said channels being substantially equal 'in length'to the flow paths in the other of said chan 1 "3. The-heatexchange apparatus as defined in claim 2,

wherein the main supply and return conduits are concenftric' wi th the inner and outer drier shells and the branch supply "and return conduits extend radially from the main conduits.

4. The heat exchange apparatus as defined in claim 3, including axles fixed to the end walls of said di'iers, said axles having passages there through communicating with said main conduits.

' 5. The heat exchange apparatus as defined in claim 2, wherein the longitudinal centerlines of said branch supply conduits'and of said branch return conduits are in two separate planes, said planes being substantially parallel to, on opposite sides of, and substantially equally far from a plane through the longitudinal midpoint of and normalto s'aid drier shells. 1 g

' 6; The heat exchange apparatus as defined'in claim 2, wherein the branch supply conduits and branch return 'conduitscornlnunic'atingwith each' of said flow channels are substantially equiangularly spaced, whereby the flow paths in each of said channels are of substantially equal length.

' 7. The heat exchange apparatus as defined in claim 2, wherein: p

(a) theinletsand outlets to and from the branch re turnand branch supply pipes, respectively, communicateWith said channels at about the midpoints of said passages; and

i (b) said inlets and outlets are arranged in inlet-outlet pairs with an inlet'to one of said channels and an outle'tto another'of said channels communicating with adjacent ones of said passages.

References Cited by the Examiner UNITED STATES PATENTS CHARLES SUKALO, Primary Examine}. 

1. HEAT EXCHANGE APPARATUS ADAPTED TO HAVE A FLUID HEAT TRANSFER MEDIUM CIRCULATED THERETHROUGH TO HEAT AN EXTERNAL SURFACE OF SAID APPARATUS TO A UNIFORM PREDETERMINED TEMPERATURE, COMPRISING: (A) CONCENTRIC INNER AND OUTER SHELLS OF SUBSTANTIALLY EQUAL LENGTH, SAID SHELLS HAVING A UNIFORM THICKNESS AND THE RADIAL DISTANCE BETWEEN SAID SHELLS BEING SUBSTANTIALLY GREATER THAN THE THICKNESS OF EACH OF SAID SHELLS; (B) FIRST AND SECOND END WALLS AT THE OPPOSITE ENDS OF AN EXTENDING BETWEEN THE INNER AND OUTER SHELLS, SAID END WALLS BEING FIXED TO SAID SHELLS TO PROVIDE A CLOSED ANNULAR PASSAGE THEREBETWEEN; (C) RADIALLY ORIENTED, LONGITUDINALLY EXTENDING PARTITIONS WHICH ARE MEMBERS SEPARATE FROM SAID SHELLS BETWEEN AND FIXED TO SAID SHELLS, THE ENDS OF ALTERNATE PAIRS OF SAID PARTITIONS BEING CLOSELY ADJACENT THE FIRST END WALL AND SUBSTANTIALLY SPACED FROM THE SECOND END WALL, AND THE ENDS OF THE PAIRS OF PARTITIONS BETWEEN SAID ALTERNATE PAIRS BEING CLOSELY ADJACENT THE SECOND END WALL AND SUBSTANTIALLY SPACED FROM THE FIRST END WALL; (D) A PLURALITY OF FLUID CONDUCTING MEANS IN THE INTERIOR OF SAID OUTER SHELL FOR CONDUCTING FLUID FROM THE ENDS OF PASSAGES FORMED BY THE SHELLS AND PARTITIONS TO THE NEXT ALTERNATE PASSAGE AND THEREBY DIVIDING THE PASSAGES BETWEEN PARTITIONS INTO TWO INDEPENDENT LABYRINTHINE FLOW CHANNELS WITH ADJACENT PASSAGES BEING IN DIFFERENT ONES OF SAID FLOW CHANNELS, SAID FLUID CONDUCTING MEANS HAVING FIRST AND SECOND LEGS EXTENDING THROUGH SAID INNER SHELL AND BEING IN FLUID COMMUNICATION WITH THE PASSAGE BETWEEN THE PARTITIONS IN A FIRST ONE OF SAID PAIRS AND THE PASSAGE BETWEEN THE PARTITIONS IN THE ADJACENT ONE OF SAID PAIRS, THE LEGS OF SAID FLUID CONDUCTING MEANS FORMING CLOSURES FOR THE ENDS OF THE PASSAGES WITH WHICH SAID LEGS COMMUNICATE, ONE OF SAID LEGS BEING SPACED FROM THE NEAREST END WALL AND THE OTHER OF SAID LEGS BEING IN CONTACT WITH THE NEAREST END WALL, WHEREBY THE PASSAGES BETWEEN ADJACENT PAIRS OF PARTITIONS ARE SERIALLY CONNECTED TO FORM ONE OF SAID CHANNELS AND THE PASSAGES BETWEEN THE PARTITIONS IN THE PAIRS OF PARTITIONS ARE SERIALLY CONNECTED TO FORM THE OTHER OF SAID CHANNELS; (E) MEANS FOR DIRECTING FLUID TO EACH OF SAID CHANNELS; AND (F) MEANS FOR CONDUCTING FLUID FROM EACH OF SAID CHANNELS. 